1. Technical Field
The present invention relates to a liquid crystal display device and to an electronic apparatus, and more specifically, to a technique for achieving display having high brightness and a wider viewing angle both in a reflective mode and in a transmissive mode in a transflective color liquid crystal display device using vertical-alignment-type liquid crystal.
2. Related Art
Transflective liquid crystal display devices having both a reflective mode and a transmissive mode have been generally known as liquid crystal display devices. As the transflective liquid crystal display device, a display device has been suggested in which a liquid crystal layer is interposed between an upper substrate and a lower substrate, and a reflective film obtained by forming light-transmissive windows in a metal film made of, for example, Al, is provided on an inner surface of the lower substrate to function as a transflective sheet. In this case, in the reflective mode, external light incident on the upper substrate passes through the liquid crystal layer and is then reflected from the reflective film on the inner surface of the lower substrate. Then, the reflected light passes through the liquid crystal layer again to be emitted from the upper substrate, thereby contributing to display. On the other hand, in the transmissive mode, light emitted from a backlight to the lower substrate passes through the liquid crystal layer via the windows of the reflective film, and is then emitted from the upper substrate to the outside, thereby contributing to display. Therefore, in a region where the reflective film is formed, a portion thereof where the window is formed serves as a transmissive display region, and the other portion serves as a reflective display region.
However, this type of transflective liquid crystal display device has a problem in that a viewing angle is narrow in the transmissive display. The reason is that, since the transflective plate is provided on an inner surface of a liquid crystal cell to prevent the occurrence of parallax, reflective display should be performed by using only one polarizing plate provided on an observer side, which results in a low degree of flexibility in the optical design. Therefore, in order to solve this problem, the inventors, M. Jisaki et al., have proposed a liquid crystal display device using vertical-alignment-type liquid crystal as disclosed in “Development of transflective LCD for high contrast and wide viewing angle by using homeotropic alignment,” M. Jisaki et al., Asia Display/ID W′01, pp. 133 to 136 (2001). The liquid crystal display device has the following three features:
(1) A ‘VA (vertical alignment) mode’ is used in which liquid crystal molecules having negative dielectric anisotropy are vertically aligned with respect to substrates in an initial state, and are then inclined when a voltage is applied;
(2) A ‘multi-gap structure’ is used in which the thickness (cell gap) of a liquid crystal layer in a transmissive display region is different from that in a reflective display region (for example, see Japanese Unexamined Patent Application Publication No. 11-242226); and
(3) An ‘alignment dividing structure’ is used in which each transmissive display region is formed in the shape of a regular octagon, and a projection is provided at the center of the transmissive display region on a counter substrate to make the liquid crystal molecules incline in all directions in the transmissive display region.
The transflective liquid crystal display device having the multi-gap structure, disclosed in Japanese Unexamined Patent Application Publication No. 11-242226, has an advantage in that electro-optical characteristics (a transmittance-voltage characteristic and a reflectance-voltage characteristic) of the reflective display region are identical to those of the transmissive display region. The reason is that light passes through the liquid crystal layer one time in the transmissive display region, but it passes through the liquid crystal layer two times in the reflective display region.
However, in the paper of Jisaki et al., the directions in which the liquid crystal molecules in the transmissive display region are inclined are controlled by a projection provided at the center of the transmissive display region. However, the paper does not disclose how to control the directions in which the liquid crystal molecules in the reflective display region are inclined at all. When the directions in which the liquid crystal molecules are inclined are not controlled, the liquid crystal molecules are inclined in random directions. In this case, a line of discontinuity, referred to as disclination, appears at boundaries between different liquid crystal alignment regions, which causes residual images. Also, since the alignment regions of the liquid crystal have different viewing angle characteristics, a spotted pattern may appear when the liquid crystal device is viewed from an oblique direction. In addition, it is considered that alignment regulators, such as projections, are provided in the reflective display regions. However, since the reflective display region has a narrower gap than the transmissive display region, alignment disorder of the liquid crystal occurs due to the alignment regulators when the alignment regulators are provided in the narrow gap.